Prayer Shawl
There are multiple variations of the Prayer Shawl quest throughout the game. The first one starts during Velious, the second one during Underfoot and the third one during Rain of Fear. I am sure there will be another one in the future but who knows when. Depending on your server and you, you may have to do them all or just the third one. Players on FV are able to buy the Blessed Underfoot Prayer Shawl which negates the whole need to do the Coldain Shawl 2 quest.
The third Prayer Shawl is one of the best min/max things to do for a lot of classes considering the fact that it's an aug with a great proc on it. All three of these quests will require you to do some tradeskills and all three of them are primarily tradeskill quests, much like the Artisan's Prize is.
I don't know much about the first two quests since I play on FV (I know, I know) but the third one picks up in Plane of Knowledge at the small bank. In order to start the quest you'll need to have 300 skill in each of the seven major tradeskills. Baking, Brewing, Fletching, Jewelcrafting, Pottery, Tailoring, Smithing. That'll allow you to start the chain of quests which you won't be able to complete alone. One of the last things you need to do is collect Brell's Shadow, an item from the Plane of Fear raid during the Rain of Fear expansion.